The present invention relates generally to torque limiters for preventing damage to mechanical actuation systems, and, more particularly, to an improved torque limiter in which the setting of a variable (e.g., maximum torque) is set upon, or as a condition precedent to, installation of a mechanical module on a supporting body.
It is known to provide torque limiters to prevent damage to the components of a mechanical actuation system in the event of a jam. One example of such a system would be the leading edge slat system for an aircraft. In this system, power in the form of mechanical torque and rotary motion is transmitted by a torque shaft along the leading edge of an aircraft wing. Power is extracted from the torque shaft by a series of geared mechanical actuators at various locations spaced there along, and is used to drive several slat surfaces simultaneously. There may be one or more actuators per slat surface, and each actuator is typically protected by a torque limiter that is set to transmit torque to the associated actuator that is sufficient to overcome anticipated normal operating loads but it is not large enough to damage the actuator or any other part of the system in the event of a jam. Typically, these slat surfaces differ widely in area. Hence, the operating loads to which the various torque limiter are set, will vary similarly.
The prior art contemplates the use of a different torque limiter for each actuator, with an operating cost penalty because of the lack of a common component, or the use of a common component at each location with a structural weight penalty in those parts of the system where the surfaces and loads are smaller. Heretofore, it has been thought that a common manually-adjustable torque limiter that would be replaceable in the field, could not be used for safety reasons.
With parenthetical reference to the corresponding parts, portions or surfaces of the disclosed embodiment, merely for purposes of illustration and not by way of limitation, the present invention, in one aspect, provides an improvement in a mechanical module (e.g., 20 in FIG. 1) that is adapted to be interchangeably mounted on a body (21) at a particular location. The body has at each of the locations a particular geometry that cooperates with the module to mandate the relative position of the module with respect to the body at such location. The module has a housing (28) adapted to be mounted on the body and has a setting member (32) that is movable relative to the housing within a permissible range of movement to set a functional variable characteristic (e.g., torque) of the module. The improvement broadly comprises: the setting member engaging the body geometry at any of such locations at only one permissible relative position within the range when the module is mounted on the body at such location; the value of the variable characteristic being determined by the position of the setting member relative to the housing when the module is mounted on the body at such location; whereby the variable characteristic will be determined automatically either during, or as a condition precedent to, mounting the module on the body.
The location mentioned above may possibly be one of a plurality of locations. In this event, each location may have a different and unique mounting geometry that is largely a function of the anticipated load. If the anticipated load differs at each location, then the mounting geometry between the body and module will be different at each location to insure that the variable characteristic is properly set for the anticipated load at that location. However, if the anticipated load is the same at each of two locations, then the mounting geometry may be the same at those locations.
In another aspect, the improvement comprises: the value of the variable characteristic being determined by the position of the setting member relative to the body, as constrained by the body geometry at any such location, the setting member and body being so configured and arranged as to permit the module to be mounted on the body at any such location only when the setting member is in the preselected position for such location, and to prevent the module from being mounted on the body when the setting member is in a position other than the preselected position for such location; whereby the module is prevented from being mounted on the body unless the setting member is in the preselected position.
In still another aspect, the invention provides a torque-limiting module adapted to be mounted on a body at any of a plurality of locations, the body having at each location mounting features (85) that mandate the relative position and orientation of the module relative to the body. The improved module comprises: a housing (28) adapted to be mounted on the body; an input shaft (22); an output shaft (29); a coupling (30) between the shafts; a brake (31) arranged to act between the housing and the output shaft for selectively braking the shafts when the torque transmitted by the output shaft exceeds a predetermined torque value; a cam surface (25) mounted on the body at each of the locations; and a cam follower (32) mounted on the module for movement along an axis, and engageable with the cam surface at any location. The module is operatively arranged to selectively set the predetermined torque value as a function of the position of the cam follower relative to the module; whereby the predetermined torque value is set, either automatically during, or as a condition precedent to, mounting the module on the body at any of such locations.
Accordingly, the general object of this invention is to provide an improved torque limiter.
Another object is to provide an improved torque-limiting module that has a settable variable characteristic, such as maximum torque, and that may be mounted at any of a number of locations on a body.
Another object is to provide a common torque limiter that is adapted to be mounted on a body at any of a plurality of locations, and in which the maximum torque is individually determined by the particular mounting geometry between the module and body at a given location.
Another object is to provide an improved torque limiter in which the value of maximum torque is determined automatically upon the mounting of the module on a body.
Another object is to provide an improved torque limiter in which the value of maximum torque must be determined as a condition precedent to mounting the module on a body.
Still another object is to provide an improved torque limiter that is adapted to be mounted on a body at any of a plurality of locations and which requires that a characteristic, such as maximum torque, be set as a function of the geometry of the particular location at which the module is mounted on the body.
These and other objects and advantages will become apparent from the foregoing and ongoing written specification, the drawings, and the appended claims.